Controlling atmospheric conditions



Oct. 14, 1 969 TAYLQR 3,472,040

CONTROLLING ATMOSPHERIC CONDITIONS Filed July 5. 1967 I? 'ENTOR.

Da v/d H. Taylor M5665 m flzw'w ATTORNE YS United States Patent US. Cl.62-117 5 Claims ABSTRACT OF THE DISCLOSURE The temperature and/orhumidity within an enclosure may be controlled by alternately coolingand heating the space, but in which the extent of the heating phase ofthe cycle is limited and controlled.

This invention relates to improvements in a method and means ofcontrolling atmospheric conditions within an enclosure. In general, theinvention is concerned with controlling the temperature and/or humiditywithin an enclosure used for the preservation of perishable commodities,and more particularly when such goods are being transported forsubstantial periods of time.

Although it is customary to store or transport perishable commodities inenclosures which are refrigerated, and which are also insulated,variations in weather conditions can affect the atmospheric conditionswithin the enclosure, and this is particularly true in the instance ofan insulated carrier. When goods are transported for considerabledistances, either by land or by sea, they will pass through zones wheretemperature and humidity conditions are very likely to change, andthereby affect the conditions in the cargo carrying space.

It is known in the prior art to provide a method and means ofmaintaining a substantially constant temperature within an enclosureused to transport perishable products, and one example is found in thedisclosure of US. Patent 2,992,541, assigned to the present assignee.According to that patent, the enclosed space is cooled to apredetermined minimum temperature, and then the system is modified toraise the temperature within the controlled space. By this arrangementof alternate heating and cooling, proper compensation can be had withoutregard to the ambient temperature, for if the ambient temperature ishigh, the system continues to cool sufliciently to compensate for heatleakage into the enclosure, whereas if the ambient temperature isexcessively cool, the heating phase of the cycle will add sufiicientheat to compensate for heat losses from the enclosure.

While the system described above will maintain a reasonable uniformtemperature, there may be conditions under which improvements aredesired, as for example, when the cargo space within the enclosure hasbeen charged with an artificial atmosphere, such as nitrogen. It is wellknown that many forms of food products undergo respiration, and in someinstances, the intake of oxygen from ordinary air is undesirable, and insuch circumstances, an artificial atmosphere, is used. In the alternateheating and cooling that occurs in the manner previously described, theheating cycle causes an expansion of the internal atmosphere, therebyproducing leakage at doors, drain tubes or other openings in theenclosure. Then, when the unit switches to cooling the internalatmosphere contracts and sucks in outside air to replace the nitrogen orother gas that Was lost in expansion. Hence, if an artificial atmosphereis used, the alternate heating and cooling thereof will soon bring intothe enclosure undesired atmospheric air.

Another condition where the normal heating and cooling, as previouslydescribed, may be undersirable, is in the instance where temperaturechange to commodities close to the heat exchanger may be harmful. Itwill be recognized that with alternate heating and cooling, the portionof the goods which is located in close proximity to the heat exchangeelement may be subjected to a greater range of temperature change thanthose goods which are more distantly located from the heat exchanger.With some products, such a degree of temperature variation may result indehydration of the product.

A further condition that may be undesirable can occur Where the goodsare of a nature such that they can be injured by the presence of anexcessive amount of humidity. Some forms of meat products will nottolerate an excessive amount of moisture, and when that conditionexists, an undesirable slimy surface may be formed on the product.

An object of the inventory is to provide a method of controlling acondition of the atmosphere within an enclosed space by controlling therate of heating of said enclosed space in a system which continuouslyand alternately heats and cools the space to approximate a desiredtemperature therein.

Another object is to so reduce the heating effect in a system designedto alternately heat and cool an enclosed space to the extent that theheating is negligible and has substantially the same effect as shuttingthe system off during that portion of the alternate action devoted toheating.

Another object is to control the humidity conditions within an enclosedspace by the use of a system designed to alternately cool and heat thespace, and wherein the heating step has the additional effect ofaccentuating the cooling step to remove moisture from the atmosphere.

Other and further objects may become apparent from the followingspecification and claims, and from the appended drawing, in which thesingle figure is a schematic diagram of a refrigeration system andcontrols embodying one form of the present invention.

Referring now to the single figure of the drawing, the structure formingthe apparatus of this invention will be described in detail.

General reference numeral 10 indicates in its entirety a refrigerationsystem. The system includes a compressor 12 driven by a prime mover 14,which may be either an electric motor or an internal combustion engine.Extending from the high pressure side of the compressor 12 is a conduit16 which extends to a condenser 20 and contains a three-way valve 18.The discharge side of condenser 20 contains a check-valve 22 and extendsto a receiver 24. A conduit 26 extends from receiver 24 to an evaporator28 and contains a dehydrator 30, a valve 32, and at the juncture betweenconduit 26, and the evaporator coil 28, is a thermostatic valve 34 whichis controlled by a thermostatic element 36 that is in thermal contactwith a portion of the evaporator 28. A conduit 38 extends from theoutlet end of the evaporator coil 28 to an accumulator 40, and theoutput side of the accumulator 40 is connected by a conduit 42 whichextends to the low pressure side of compressor 12. Operably associatedwith the accumulator 40, for the purpose of evaporating any liquidrefrigerant that may be present in the accumulator, is a source of heatherein indicated as an engine muffler 44, which through a pipe, aportion of which is indicated at 45, extends from the prime mover 14.Thermostatic control means operably connect the mufiler 44 with theaccumulator 40 to control the heating of the accumulator 40, and hencethe rate of evaporation of refrigerant, as disclosed in my prior Patent3,219,102.

The condenser 20 and evaporator 28 'are each schematically disclosed ascomposed of a single coil, while in practice they are, in fact, composedof many coils, and may be disposed as a unitary structure divided by aninsulated wall, as shown in US. Patent 2,336,735. The evaporator coil 28has associated with it a fan or blower 46, and these two structures aredisclosed within a casing 48 disposed within an insulated enclosure 50.The casing 48 has an inlet opening 52 whereby the fan 46 draws air fromwithin the interior of the enclosure 50 and discharges the same intothermal contact with evaporator 28, and thence back to the interior ofenclosure 50 through an Outlet opening 54.

A conduit 56 extends from valve 18 to a T 58. From one side of T 58 aconduit 60, containing a check valve 62, extends to a T 64 interposed inthe discharge side of condenser 20. From the T 58, a conduit 66 extendsto a T 68 disposed adjacent the inlet end of evaporator 28, and beyondthe thermostatic valve 34.

interposed in the conduit 26, between valve 32 and the expansion valve34, is a T 70 which extends to a pressure responsive motor 72, heredisclosed as a bellows, whose interior is in communication with theconduit 26, and responsive to the pressure therein, in contrast toatmospheric pressure on the outside of the bellows. The pressure motor72 is joined to a switch arm 74, which is pivoted at 76 and has acontact 78 that moves relative to a contact 80. Movement of the pressuremotor 72, and hence the switch arm 74 is subject to control by a spring82, whose pressure is made adjustable by an adjusting member 83.

An electrical system is provided for operating certain control portionsof the system, and these include a source of power, indicated by battery84, from which a conductor 86 extends to a coil 88 surrounding anarmature 90 that actuates valve 32. From the coil 88, a conductor 92extends through a thermostatic switch 94 to ground. The switch 94 islocated within the enclosure 50, and is of the type whose contacts closeon a temperature drop within the enclosure 50 to energize the armature90 and move the control mechanism of valve 32 to a closed position tothereby terminate the flow of refrigerant fluid through conduit 26between receiver 24 and the evaporator 28. A second conductor 96 extendsfrom battery 84 to contact 78. A conductor 98 extends from contact 80 toa coil 100 that surrounds an armature 102 which is connected to theactuating member of valve 18.

The operation of the system herein described will now be explained. Itmay be assumed that the prime mover 14 is in operation, and iscontinuously driving the compressor 12. Assuming further that thetemperature within enclosure 50 is above a predetermined desiredtemperature, the refrigeration system is operating in its normalrefrigerating cycle. Refrigerant fluid flows from the receiver 24through the conduit 26 to and through the dehydrator 30, valve 32, valve34 into the evaporator 28, where it evaporates, drawing heat from thespace. Thence the vapors return through conduit 38, accumulator 40,conduit 42 to the compressor. The compressed fluid flows through conduit16, passing through valve 18 to the condenser 20 and hence through thecheck-Valve 22 and T 64 to the receiver 24.

After the space within the enclosure 50 is cooled to the desiredtemperature, the contacts of thermostat 94 close to complete a circuitfrom battery 84 to ground, which energizes the solenoid valve 32, movingthe same to a closed position, and thereby terminating the flow ofrefrigerant fluid in the normal course to the evaporator 28. With thefluid circuit blocked by the valve 32, the continuously operatingcompressor removes refrigerant from the evaporator 28, progressivelydiminishing the pressure in the system on the side beyond valve 32. Thepressure motor 72 has up to this time been subjected to the higherpressure within the refrigerant sys tem in contrast to the lowerpressure of atmosphere, but as the internal pressure continues todiminish, and

under the influence of the spring 82, the pressure motor 72 willcontract until the switchblade 74 brings contact 78 into engagement withcontact 80. When this occurs, a second circuit is closed between thebattery 84 and the electrical motor 100, 102, that actuates valve 18,and the actuation of this valve cuts off the fiow of the compressedrefrigerant from conduit 16 to the condenser 20, and diverts this flowthrough the conduit 56 to the T 58. and because of the low pressure inthe evaporator, all of the flow will be diverted through conduit 66 tothe evaporator, and thence through the return conduits 38 and 42 to thecompressor. The action of by-passing the compressed refrigerant to theevaporator will cause a heating of the evaporator to the extent of theenergy transferred to the refrigerant fluid by the compressor. Thedegree or rate of heating produced by this arrangement is proportionalto the amount of refrigerant that is undergoing circulation. Thus, if asubstantial quantity of refrigerant has been removed from the circuitbefore the modification in the flow path caused by the actuation ofvalve 18, there will be a diminished quantity of fluid circulatingthrough the system, and therefore, only a limited amount of heating willoccur. The system continues to operate in this manner until the heatgiven off by the evaporator 28 is sufficient to raise the temperature inthe controlled space 50 to a point where the contacts of thermostat 94are opened. When the thermostat 94 opens, the circuit is broken to valve32, which opens under the influence of a spring (not shown) and permitsflow of refrigerant fluid through conduit 26 to the evaporator 28 toraise the pressure suflicient to break engagement between the contacts78 and 80, and reinitiate the refrigerating cycle,

The system is subject to control by the adjustment of the member 83relative to spring 82. By increasing the pressure on spring 82, thesensible heat within the system can be increased and will cause a longerrunning of the system on the refrigeration cycle which, in turn, willcause moisture to condense or freeze on the evaporator coil fordisposition in a subsequent defrosting operation.

It follows from the foregoing discussion taken in conjunction with thedescription that the system tends, with a continuously operating system,to maintain a substan- L tially constant temperature within the enclosedspace by intermittent cooling operations separated by periods of slightheating, which are sufficient to aid in moisture control, as well astemperature control. This system is considerably different from merelyshutting down the refrigeration system when a desired temperature isreached, because it permits continuous circulation of the atmosphere,and it also provides humidity control.

The invention is defined in the appended claims.

I claim:

1. In a process of heat exchange between an external environment and thespace within an enclosure which embodies:

disposing a closed circuit heat transfer system, including a compressor,condenser, receiver and evaporator, said system having a first portionto include said evaporator located in heat exchange relationship withthe space within said enclosure and a second portion to include saidcondenser located in heat exchange relationship with said externalenvironment;

passing a heat exchange fluid through said first portion of said systemat temperatures alternately above and below the space temperature inresponse to a condition of the atmosphere within said enclosure; theimprovement of progressively reducing the quantity of said fluid whichis circulated within said first portion of said system when thetemperature of said fluid within said first portion is above the spacetemperature and when no further heat transfer to said space is requiredby the condition of the atmosphere within said enclosure until thequantity of said fluid which remains in circulation in said system isthe minimum necessary to maintain an operative condition of said systemincluding said compressor;

isolating in said receiver and condenser by the sequential operation ofvalves that portion of said heat exchange fluid which is not maintainedin circulation in said system;

and circulating the reduced quantity of said fluid through a portion ofsaid system including said compressor and evaporator, the reducedquantity of fluid thereby providing negligible heat transfer to thespace until the condition of the atmosphere within said enclosure whichcontrols the system varies from a predetermined condition.

2. A process according to claim 1, in which the condition of theenclosed atmosphere which is controlled is the humidity thereof.

3. A process according to claim 1, in which the condition of theenclosed atmosphere which is controlled is the temperature thereof.

4. A process according to claim 1 in which the control of the flow ofthe fluid during the high temperature thereof is in response to thepressure of said fluid within the heat exchange member.

5. Apparatus for controlling an atmospheric condition within an enclosedspace, embodying a mechanical refrigeration system including anevaporator, a condenser,

a compressor joined between the outlet of said evaporator and the inletof said compressor, a receiver, a first conduit including an expansionvalve joined between said receiver and the inlet end of said evaporator,a valve disposed in said fluid conduit between said receiver and saidexpansion valve, a second conduit forming a hot gas by-pass between thedischarge end of said compressor and said evaporator, a valve in saidsecond conduit, and a pressure responsive means operably connected tothe first fiuid conduit between the expansion valve and the first namedvalve and operably connected to said valve in said second conduit forcontrolling the actuation thereof in response to the fluid pressurewithin said first conduit.

References Cited UNITED STATES PATENTS 2,992,541 7/1961 Sutton 62-1173,219,102 11/1965 Taylor -2 3,332,251 7/1967 Watkins 62-197 X 3,350,89511/1967 Hamish 62-197 3,358,923 12/1967 Stedman 236-46 ROBERT A. OLEARY,Primary Examiner ALBERT W. DAVIS, Assistant Examiner US. Cl. X.R. 62174,197; 1652, 31

